Ionic liquids are liquids composed of ions that are liquid at temperatures of 100° C. or below. The very low vapour pressure, high thermal stability, and tuneable miscibility with other liquid phases that characterizes ionic liquids renders them interesting as alternatives to traditional organic liquids for several applications, including reaction media in synthesis, electrolytes in electrochemical processes or media in separation or analytical techniques.
Ionic liquids generally consist of an organic cation bearing alkyl substituents of variable chain length and an inorganic or organic anion. Among the most common cations, mention can be made of quaternary ammonium or phosphonium ions, N,N′-dialkylimidazolium, N-alkylpyridinium, N,N′-dialkylpyrrolidinium and guanidinium. Common anions are for instance BF4−, halogenides (Cl, Br, I), PF6−, carboxylates, alkylsulfonates, alkylsulfates, and thiocyanates.
Ionic liquids comprising a fluoroalkylsulfonate ion are known, see for instance US 20070100184 (DU PONT DE NEMOURS) May 3, 2007 and KULKARNI, P. S., et al. Comparison of physicochemical properties of new ionic liquids based on imidazolium, quaternary ammonium and guanidinium cations. Chem. Eur. J. 2007, vol. 13, p. 8478-8488.
Fluoroalkylsulfonate salts may also find use as surfactants.
Several processes have been described for the preparation of quaternary ammonium or guanidinium fluoroalkylsulfonate salts. In the references cited above the preparation involves an anion exchange, typically starting from the chloride of the quaternary ammonium or guanidinium cation.
More complex routes for the synthesis of the trifluoromethansulfonate salts have been described in KUNKEL, H., et al. Hexaalkylguanidinium trifluormethanesulfonate—A general synthesis from tetraalkylureas and triflic anhydride, and properties as ionic liquids. Eur. J. Org. Chem. 2007, p. 3476-3757., IGNAT'EV, N., et al. A convenient synthesis of triflate anionic liquids and their properties. Molecules. 2012, vol. 17, p. 5319-5338, and in US 20070265453 (MERK PATENT GMBH) Nov. 15, 2007.
None of these processes however disclose the preparation of fluoroalkylsulfonate salts of a wide array of nitrogen-based organic bases by a one pot reaction of a fluoroalkylsulfonyl halide with the nitrogen-based organic base.
BURDON, J., et al. Trifluoromethane sulfonate esters and their alkylating properties. Tetrahedron. 1965, vol. 21, p. 1-4, relates to the alkylating properties of trifluoromethanesulfonate esters. This document discloses the reaction of trifluoromethanesulphonyl fluoride with alcohols in the presence of pyridine; in particular, this document discloses the reaction of trifluoromethanesulphonyl fluoride with ethanol in the presence of pyridine to provide ethylpyridinium trifluoromethanesulfonate.
DE 1966931 (BAYER AG) May 28, 1975 discloses the synthesis of ammonium salts of general formula:[R1R2R3R4N]+[RfSO3]−wherein:—R1-R4 represent alkyl, alkenyl, cycloalkyl or alrylalkyl, or together with the N atom they are bound to, form a heterocyclic ring, and Rf represents C1-C12 perfluorinated straight or branched alkyl. These salts are prepared by reaction of a tertiary amine, a perfluorinated sulfonyl fluoride and a silane ester. The reaction can be carried out in the presence of a polar inert solvent, like an ether, chloroform or acetonitrile.
U.S. Pat. No. 4,168,277 (BAYER AKTIENGESELLSCHAFT) Sep. 18, 1979 discloses a process for the synthesis of a tetraethylammonium perfluoroalkyl sulfonate comprising reacting a perfluoroalkyl sulfonyl fluoride with triethylamine and an ethoxysilane in an inert solvent medium like chlorobenzene, ethers and toluene (col. 2, lines 53-54). The examples teach the use of chlorobenzene.
EP 0726249 A (HALDOR TOPSOE A/S) Aug. 14, 1996 discloses a process for base hydrolysis of a fluorinated sulfonyl fluoride with at least one mole equivalent of water and a tertiary amine to provide a salt of a corresponding fluorinated sulfonic acid with the amine.
EP 036094 A (MINESOTA MINING AN MANUFACTURING COMPANY) Apr. 11, 1990 discloses fluorochemical surfactants that are prepared by reacting at least one perfluoroalkyl sulfonyl fluoride having 3 to 20 carbon atoms, ethylene or propylene oxide, and at least one tertiary amine. It stems from the examples that the reaction occurs in the absence of solvents.
TAKAHASHI, K., et al. Development of triaryalmine mediator having ionic-tag and its application to electrocatalytic reaction in an ionic liquid. Electrochimica Acta. 2012, vol. 77, p. 47-53, discloses a process for the synthesis of:                a trifluoromethanesulfonate salt of 4-[bis(4-bromophenyl)amino]benzyl triethylammonium and:        a trifluoromethanesulfonate salt        of 1-{4-[bis(4-bromophenyl)amino]benzyl}-3-methyl-imidazolium by reaction of of 4-[bis(4-bromophenyl)amino]benzyl alcohol, trifluoromethanesulfonyl chloride and triethylamine or 1-methyl imidazole in the presence of methylene chloride as the solvent.        